The Children of Israel spent forty years wandering in the desert before they came to the Promised Land. (Some say that’s because they got lost, which in turn is because men are always too proud to ask for directions.) Some of the Israelites gave up hope of ever arriving and wished they’d stayed in Egypt rather than following Moses out and across the Red Sea as the waves parted. Yet they reached their destination in the end and lived happily ever after… well, almost. We’ve just celebrated their escape from Egypt as we do each year on Seder night – the first night of Passover.

But that’s not the forty years I meant.

Alan Bennett’s first West End play was called Forty years On.

No, not that either.

This is it: Forty years ago, David Drori placed this ring on my finger and we’ve been together ever since… he and I, that is. The ring and I, too, but that’s less important.

When exactly did that happen? This is where things get complicated. The date we remember is 11th April. In fact it’s more than what we remember; it’s the actual date. But is that the date we should be celebrating?

I didn’t really colour my hair for the wedding. The scanning process changed its colour.

One year, when we were both working in the same office and mentioned it was our anniversary, someone remarked, “This is why you should celebrate the Hebrew date and not the Gregorian date.”

We probably looked confused and she added, “You didn’t get married after Pesach (Passover) did you?”

The asimon dropped. (That’s the literal translation of the Hebrew expression. An asimon was a telephone token, used in public phones instead of coins, probably because of rampant inflation at that time.) No, of course we didn’t. Jews don’t get married from the beginning of Passover for at least thirty-three days (depending on their branch of Judaism) because of the Omer, which is like Lent, I think. But as Jewish festivals take place according to the Hebrew calendar, they vary according to the Gregorian calendar. In 1978, 11th April fell more than a week before Passover. Most years, Passover begins before it.

How does the Hebrew calendar work? A year usually has twelve months, the names of which I learned to recite at the age of five and still remember. Every so often, according to a calculation I don’t remember, there’s a leap year during which a whole month is added.

David has no trouble remembering the Hebrew date of his birthday. He was born on the eve of Passover and was pleased to discover that this year his Gregorian and Hebrew birthdays coincided.

The modern State of Israel mostly works according to the Gregorian calendar. Things would get confusing if we didn’t. And that’s why we don’t remember the date of our wedding according to the Hebrew calendar, although this year it was probably at around the time we celebrated it with a meal in Petersham Nurseries, Richmond Park, UK, before we left for another trudge through the snow.

One thing I can be sure of: There will be no snow when we celebrate again, in Jerusalem, on 11th April.